A real-time PCR assay for detection of Rickettsia rickettsii to aid in vivo infection monitoring.

Rocky Mountain spotted fever (RMSF) is an important and potentially fatal tick-borne disease impacting people and dogs. RMSF, caused by Rickettsia rickettsii, is frequently reported in parts of the North, Central and South American countries. The treatment for RMSF is limited to tetracyclines, specifically to doxycycline. If untreated, the disease can progress rapidly to fatal outcomes, particularly in children. In recent years, fatality rates ranging from 30% to 80% have been reported throughout South America, Mexico, and in parts of Indian reservations in southwest regions of the USA. To aid in support of monitoring in vivo R. rickettsii infections, we developed a novel quantitative PCR (qPCR) assay to facilitate the sensitive and specific detection of R. rickettsii. The assay was designed and optimized using the surface cell antigen 4 gene as the target. The utility of the assay was defined for its specificity, analytical sensitivity, efficiency, and to monitor infections in the canine host following R. rickettsii infection challenges. With having high specificity and analytical sensitivity, the qPCR assay can be utilized for diverse research applications promoting investigations on R. rickettsii.